This Phase I application deals with non-invasive imaging of oral, nasal, and pulmonary airways. Image reconstruction is based on information contained in acoustic reflections measured at the mouth. Amplitudes and arrival times of acoustic returns permit accurate reconstruction of airway dimensions as a function of axial distance along the airway. At its current state of development this technology has been shown to be accurate, to require little subject cooperation and to have a number of diagnostic applications. However, its broader applicability has been limited by unwieldy dimensions of the apparatus, which preclude its use anywhere but in dedicated laboratories. The applicants have proposed an advanced technology that circumvents certain acoustical constraints on the minimum size of the apparatus; compared with present systems, the proposed apparatus could be smaller by more than an order of magnitude. Specific tasks would include: Development, implementation and testing of computer algorithms necessary to reconstruct airway dimensions from acoustic reflection data using the two- transducer strategy; design, build, and test a prototype apparatus with the associated software; and carry out limited tests with human volunteers to establish the new approach.